logic exprs

CHANGELOG.md

@@ -0,0 +1,8 @@
+# Changelog
+
+## 12/23/23 
+
+- Added LogicExpressions for creating and evaluating expressions 
+- Added LogicExpressions to SELECT and DELETE commands (i.e  SELECT FROM WHERE and DELETE FROM WHERE)
+- Updated SELECT formatting to pad table columns
+- General system stability improvements to enhance the user's experience.

README.md

@@ -18,7 +18,19 @@ This is a SQL database written in Rust. It will be based off of (and hopefully b
 
 [x] DELETE command
 
-[ ] WHERE clause for SELECT and DELETE
+[x] WHERE clause for SELECT and DELETE
+
+[ ] Create squirrel-core library for shared code between client & server
+
+[ ] Update parser to use common logic to identify 'objects' (i.e function calls, column references, and variables) 
+
+[ ] Move parsing to client
+
+[ ] Create better logging
+
+[ ] UPDATE command
+
+[ ] Prune deleted records from disk
 
 [ ] Primary Keys via B+ Tree
 

squirrel-client/src/main.rs

@@ -6,13 +6,15 @@ fn main() {
     match TcpStream::connect("localhost:5433") {
         Ok(mut stream) => {
             println!("Connected to Database");
-
             loop {
                 print!("SQUIRREL: ");
                 io::stdout().flush().unwrap();
 
                 let mut msg_str = String::new();
-                std::io::stdin().read_line(&mut msg_str).unwrap();
+                let bytes = std::io::stdin().read_line(&mut msg_str).unwrap();
+                if bytes == 0 {
+                    break;
+                }
                 let msg = msg_str.as_bytes();
 
                 stream.write(msg).unwrap();
@@ -32,4 +34,5 @@ fn main() {
             println!("Failed to connect: {}", e);
         }
     }
+    println!("Goodbye!");
 }

squirrel-client/test_queries.sql

@@ -0,0 +1,32 @@
+CREATE TABLE users (id int, first_name varchar 128, last_name varchar 128, address varchar 128, age int);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (1, "Alex", "Karev", "613 Harper Lane Seattle, Washington", 33);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (2, "Richard", "Hendricks", "5230 Newell Road Palo Alto, California", 24);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (3, "Dinesh", "Chugati", "5230 Newell Road Palo Alto, California", 23);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (4, "Michael", "Scott", "1725 Slough Avenue Scranton, Pennsylvania", 40);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (5, "Walter", "White", "308 Negra Arroyo Lane Albuquerque, New Mexico", 50);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (6, "Jerry", "Seinfeld", "129 West 81st Street Apartment 5A New York, New York", 38);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (7, "Elaine", "Benes", "162 Riverside Drive Apartment 3E New York, New York", 36);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (8, "George", "Costanza", "129 West 81st Street Apartment 4B New York, New York", 39);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (9, "Cosmo", "Kramer", "129 West 81st Street Apartment 5B New York, New York", 41);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (10, "Newman", "Newman", "The Postal Office, New York, New York", 45);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (11, "Frank", "Costanza", "329 West 81st Street Apartment 5A New York, New York", 68);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (12, "Estelle", "Costanza", "Del Boca Vista Phase III, Florida", 65);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (13, "Jesse", "Pinkman", "9809 Margo Street Albuquerque, New Mexico", 27);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (14, "Skyler", "White", "308 Negra Arroyo Lane Albuquerque, New Mexico", 42);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (15, "Saul", "Goodman", "160 Juan Tabo Boulevard, Suite 503 Albuquerque, New Mexico", 50);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (16, "Gus", "Fring", "Los Pollos Hermanos, Albuquerque, New Mexico", 48);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (17, "Hank", "Schrader", "4901 Cumbre del Sur Court Albuquerque, New Mexico", 43);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (18, "Wendy", "S.", "Riverside Motel, Albuquerque, New Mexico", 32);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (19, "Tuco", "Salamanca", "1230 Negra Arroyo Lane Albuquerque, New Mexico", 34);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (20, "Gale", "Boetticher", "308 Negra Arroyo Lane Albuquerque, New Mexico", 32);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (21, "Badger", "Mayhew", "RV, Somewhere in the Desert", 29);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (22, "Skinny", "Pete", "Apartment 23, Albuquerque, New Mexico", 30);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (23, "Meredith", "Grey", "Grey Sloan Memorial Hospital, Seattle, Washington", 35);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (24, "Derek", "Shepherd", "Grey Sloan Memorial Hospital, Seattle, Washington", 40);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (25, "Cristina", "Yang", "1234 Chief Webber's Apartment, Seattle, Washington", 32);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (26, "Miranda", "Bailey", "Grey Sloan Memorial Hospital, Seattle, Washington", 38);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (27, "Arizona", "Robbins", "567 Surgical Wing, Grey Sloan Memorial Hospital, Seattle, Washington", 37);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (28, "Callie", "Torres", "789 Orthopedic Wing, Grey Sloan Memorial Hospital, Seattle, Washington", 36);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (29, "Mark", "Sloan", "Grey Sloan Memorial Hospital, Seattle, Washington", 40);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (30, "April", "Kepner", "1010 Mercy West Hospital, Seattle, Washington", 30);
+INSERT INTO users (id, first_name, last_name, address, age) VALUES (31, "Jackson", "Avery", "678 Plastic Surgery Wing, Grey Sloan Memorial Hospital, Seattle, Washington", 34);

squirrel-server/src/main.rs

@@ -4,12 +4,13 @@ use std::io::{BufRead, BufReader, Read, Write};
 use std::net::{Shutdown, TcpListener, TcpStream};
 use std::thread;
 use std::collections::HashMap;
+use std::cmp;
 
 mod parser;
 pub use parser::command::Command;
 
 mod table;
-use parser::command::{CreateCommand, InsertCommand, SelectCommand, DeleteCommand};
+use parser::command::{CreateCommand, InsertCommand, SelectCommand, DeleteCommand, LogicExpression, InsertItem, LogicValue};
 pub use table::datatypes::Datatype;
 pub use table::table_definition::{ColumnDefinition, TableDefinition};
 
@@ -93,17 +94,40 @@ fn handle_delete(command: DeleteCommand) -> ::anyhow::Result<String> {
     let mut buf: Vec<u8> = vec![0; tabledef.get_byte_size()];
     let mut row_count: usize = 0;
 
-    while file.read_exact(buf.as_mut_slice()).is_ok() {
-        row_count += 1;
-    }
-
-    let _ = fs::remove_file(format!("./data/blobs/{}", command.table_name));
-
-    let _ = fs::OpenOptions::new()
+    let mut new_file = fs::OpenOptions::new()
         .create(true)
         .write(true)
         .append(true)
-        .open(format!("./data/blobs/{}", command.table_name))?;
+        .open(format!("./data/blobs/{}_new", command.table_name))?;
+
+    while file.read_exact(buf.as_mut_slice()).is_ok() {
+        let mut row_data: HashMap<String, LogicValue> = HashMap::new();
+        let mut idx: usize = 0;
+        if let Some(ref le) = command.logic_expression {
+            let mut logic_expr = le.clone();
+            for col_def in &tabledef.column_defs {
+                let len = if col_def.length > 0 {
+                    col_def.length
+                } else {
+                    1
+                };
+                let str_val = col_def.data_type.from_bytes(&buf[idx..(idx + len)])?;
+                idx += len;
+                row_data.insert(col_def.name.clone(), LogicValue::from_string(str_val)?); 
+            }
+            idx = 0;
+            logic_expr.fill_values(row_data);
+            if !logic_expr.evaluate()? {
+                new_file.write_all(&buf)?;
+                continue;
+            }
+        }
+        row_count += 1;
+    }
+    new_file.flush()?;
+
+    let _ = fs::remove_file(format!("./data/blobs/{}", command.table_name))?;
+    let _ = fs::rename(format!("./data/blobs/{}_new", command.table_name), format!("./data/blobs/{}", command.table_name))?;
 
     return Ok(format!("{} Rows Deleted", row_count));
 }
@@ -124,15 +148,10 @@ fn handle_select(command: SelectCommand) -> ::anyhow::Result<String> {
         }
     }
 
-    response += "| ";
-    for col_name in &column_names {
-        response += format!("{} | ", col_name).as_str();
-    }
-    response += "\n";
-    response += "-----------\n";
     let mut buf: Vec<u8> = vec![0; tabledef.get_byte_size()];
 
     let mut table: HashMap<String, Vec<String>> = HashMap::new();
+    let mut longest_cols: HashMap<String, usize> = HashMap::new();
     let mut num_rows: usize = 0;
 
     for col_name in &column_names {
@@ -141,6 +160,26 @@ fn handle_select(command: SelectCommand) -> ::anyhow::Result<String> {
 
     while file.read_exact(buf.as_mut_slice()).is_ok() {
         let mut idx: usize = 0;
+        let mut row_data: HashMap<String, LogicValue> = HashMap::new();
+        if let Some(ref le) = command.logic_expression {
+            let mut logic_expr = le.clone();
+            for col_def in &tabledef.column_defs {
+                let len = if col_def.length > 0 {
+                    col_def.length
+                } else {
+                    1
+                };
+                let str_val = col_def.data_type.from_bytes(&buf[idx..(idx + len)])?;
+                idx += len;
+                row_data.insert(col_def.name.clone(), LogicValue::from_string(str_val)?); 
+            }
+            idx = 0;
+            logic_expr.fill_values(row_data);
+            if !logic_expr.evaluate()? {
+                continue;
+            }
+        }
+
         for col_def in &tabledef.column_defs {
             let len = if col_def.length > 0 {
                 col_def.length
@@ -148,18 +187,36 @@ fn handle_select(command: SelectCommand) -> ::anyhow::Result<String> {
                 1
             };
             if column_names.iter().any(|col_name| &col_def.name == col_name) { 
-                let str_val = col_def.data_type.from_bytes(&buf[idx..(idx + len)])?;
-                table.get_mut(&col_def.name).unwrap().push(str_val);
+                let str_val = col_def.data_type.from_bytes(&buf[idx..(idx + len)])?.trim_matches(char::from(0)).to_string();
+                table.get_mut(&col_def.name).unwrap().push(str_val.clone());
+                longest_cols.entry(col_def.name.clone()).and_modify(|val| *val = cmp::max(*val, str_val.len())).or_insert(str_val.len());
             }
             idx += len;
         }
         num_rows += 1;
     }
 
+
+
+    // construct table string
+    response += "| ";
+    for col_name in &column_names {
+        longest_cols.entry(col_name.clone()).and_modify(|val| *val = cmp::max(*val, col_name.len())).or_insert(col_name.len());
+        response += format!("{:0width$} | ", col_name, width = longest_cols.get(col_name).unwrap()).as_str();
+    }
+    let mut total_length: usize = 1;
+    for (col_name, max_len) in longest_cols.clone() {
+        total_length += max_len + 3;
+    }
+    response += "\n";
+    for i in 0..total_length {
+        response += "-";
+    }
+    response += "\n";
     for i in 0..num_rows { 
         response += "| ";
         for col_name in &column_names {
-            response += format!("{} | ", table.get(col_name).unwrap()[i]).as_str();
+            response += format!("{:0width$} | ", table.get(col_name).unwrap()[i], width = longest_cols.get(col_name).unwrap()).as_str();
         }
         response += "\n";
     }
@@ -261,6 +318,40 @@ fn main() -> std::io::Result<()> {
     Ok(())
 }
 
+#[test]
+fn logical_expression() -> anyhow::Result<()> {
+    assert_eq!(Command::le_from_string(String::from("1 < 5")).unwrap().evaluate().unwrap(), true);
+    assert_eq!(Command::le_from_string(String::from("1 > 5")).unwrap().evaluate().unwrap(), false);
+    assert_eq!(Command::le_from_string(String::from("1 <= 5")).unwrap().evaluate().unwrap(), true);
+    assert_eq!(Command::le_from_string(String::from("1 >= 5")).unwrap().evaluate().unwrap(), false);
+    assert_eq!(Command::le_from_string(String::from("5 >= 5")).unwrap().evaluate().unwrap(), true);
+    assert_eq!(Command::le_from_string(String::from("5 <= 5")).unwrap().evaluate().unwrap(), true);
+    assert_eq!(Command::le_from_string(String::from("5 = 5")).unwrap().evaluate().unwrap(), true);
+    assert_eq!(Command::le_from_string(String::from("5 AND 5")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("5 OR 5")).unwrap().evaluate().is_ok(), false);
+
+    assert_eq!(Command::le_from_string(String::from("'Test' = 'Test'")).unwrap().evaluate().unwrap(), true);
+    assert_eq!(Command::le_from_string(String::from("'Test' = 'Text'")).unwrap().evaluate().unwrap(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' <= 'Test'")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' >= 'Test'")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' < 'Test'")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' > 'Test'")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' AND 'Test'")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' OR 'Test'")).unwrap().evaluate().is_ok(), false);
+
+    assert_eq!(Command::le_from_string(String::from("'Test' < 5")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' > 5")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' <= 5")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' >= 5")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' >= 5")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' <= 5")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' = 5")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' AND 5")).unwrap().evaluate().is_ok(), false);
+    assert_eq!(Command::le_from_string(String::from("'Test' OR 5")).unwrap().evaluate().is_ok(), false);
+
+    Ok(())
+}
+
 #[test]
 fn insert_statement() -> anyhow::Result<()> {
     let empty_statement = "";
@@ -335,5 +426,6 @@ fn insert_statement() -> anyhow::Result<()> {
         expected_output_comma
     );
 
+
     Ok(())
 }

squirrel-server/src/parser/command.rs

@@ -1,4 +1,5 @@
 use std::collections::{HashMap, HashSet};
+use std::mem;
 
 use crate::table::table_definition::ColumnDefinition;
 use crate::{Datatype, TableDefinition};
@@ -20,6 +21,7 @@ pub struct CreateCommand {
 #[derive(Debug, Eq, PartialEq)]
 pub struct DeleteCommand {
     pub table_name: String,
+    pub logic_expression: Option<LogicExpression>,
 }
 
 #[derive(Debug, Eq, PartialEq)]
@@ -32,6 +34,7 @@ pub struct InsertCommand {
 pub struct SelectCommand {
     pub table_name: String,
     pub column_names: Vec<String>,
+    pub logic_expression: Option<LogicExpression>,
 }
 
 #[derive(Debug, Eq, PartialEq)]
@@ -40,6 +43,38 @@ pub struct InsertItem {
     pub column_value: String,
 }
 
+#[derive(Debug, Eq, PartialEq, Clone)]
+enum LogicalOperator {
+    Equal,
+    GreaterThan,
+    LessThan,
+    GreaterThanEqualTo,
+    LessThanEqualTo,
+    And,
+    Or,
+}
+
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub enum LogicValue {
+    StringValue(String),
+    U8Value(u8),
+    BoolValue(bool),
+    ColumnName(String),
+}
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum LogicSide {
+   // pub expression: LogicExpression,
+    Value(LogicValue)
+}
+
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub struct LogicExpression {
+    pub left_hand: LogicValue,
+    pub right_hand: LogicValue,
+    pub operator: LogicalOperator
+}
+
 enum CreateParserState {
     Object,
     TableName,
@@ -55,12 +90,14 @@ enum SelectParserState {
     ColumnName,
     ColumnNameCommaOrFrom,
     TableName,
+    WhereKeywordOrSemicolon,
     Semicolon,
 }
 
 enum DeleteParserState {
     FromKeyword,
     TableName,
+    WhereKeywordOrSemicolon,
     Semicolon,
 }
 
@@ -77,8 +114,17 @@ enum InsertParserState {
     Semicolon,
 }
 
+#[derive(Debug)]
+enum LogicExpressionParserState {
+   NumberOrQuoteOrColname,
+   StringValue,
+   EndQuote,
+   Operator,
+}
+
+
 pub fn tokenizer(text: String) -> Vec<String> {
-    let parts = HashSet::from([' ', ',', ';', '(', ')']);
+    let parts = HashSet::from([' ', ',', ';', '(', ')', '\'']);
     let mut tokens: Vec<String> = vec![];
     let mut cur_str = String::new();
     let mut in_quotes = false;
@@ -100,10 +146,154 @@ pub fn tokenizer(text: String) -> Vec<String> {
             cur_str.push(cur_char);
         }
     }
+    tokens.push(cur_str);
 
     tokens
 }
 
+impl LogicValue {
+    pub fn from_string(string: String) -> ::anyhow::Result<LogicValue> {
+        let test = string.parse::<u8>();
+        match test {
+           Ok(u8_val) => {
+               return Ok(LogicValue::U8Value(u8_val));
+           },
+           Err(_) => {
+               let res = string.trim_matches(char::from(0));
+               return Ok(LogicValue::StringValue(res.to_string()));
+           }, 
+        }  
+    }
+}
+
+impl LogicExpression {
+    pub fn is_valid(&self) -> bool {
+        return mem::discriminant(&self.left_hand) == mem::discriminant(&self.right_hand); 
+    }
+    
+    pub fn is_evaluatable(&self) -> bool {
+        return mem::discriminant(&self.left_hand) != mem::discriminant(&LogicValue::ColumnName(String::from(""))) &&  
+                    mem::discriminant(&self.right_hand) != mem::discriminant(&LogicValue::ColumnName(String::from("")));
+    }
+
+    pub fn fill_values(&mut self, hmap: HashMap<String, LogicValue>) -> ::anyhow::Result<()> {
+        for (name, value) in hmap {
+            if self.left_hand == LogicValue::ColumnName(name.clone()) {
+                self.left_hand = value.clone();
+            }
+            if self.right_hand == LogicValue::ColumnName(name.clone()) {
+                self.right_hand = value.clone();
+            }
+        }
+        Ok(())
+    }
+
+    pub fn evaluate(&self) -> ::anyhow::Result<bool> {
+        if !self.is_evaluatable() {
+            return Err(anyhow!("Logical expression has not been properly filled. (Do you have a typo in a column name?)")); 
+        }
+        if !self.is_valid() {
+            return Err(anyhow!("Logical expression is comparing 2 differing datatypes")); 
+        }
+        println!("{:?}", self);
+        match self.left_hand {
+            LogicValue::StringValue(_) => {
+                return self.evaluate_string();
+            }
+            LogicValue::BoolValue(_) => {
+                return self.evaluate_bool();
+            }
+            LogicValue::U8Value(_) => {
+                return self.evaluate_u8();
+            }
+            LogicValue::ColumnName(_) => {
+                return Err(anyhow!("Cannot compare names of 2 columns, only values"));
+            }
+        }
+    }
+
+    fn evaluate_string(&self) -> ::anyhow::Result<bool> {
+        match self.operator {
+            LogicalOperator::Equal => {
+                return Ok(self.left_hand == self.right_hand);
+            }
+            _ => {
+                return Err(anyhow!("Invalid operator for datatype varchar"));
+            }
+        }
+    }
+
+    fn evaluate_bool(&self) -> ::anyhow::Result<bool>{
+        match self.operator {
+            LogicalOperator::Equal => {
+                return Ok(self.left_hand == self.right_hand);
+            }
+            LogicalOperator::And => {
+                if let LogicValue::BoolValue(left) = self.left_hand {
+                    if let LogicValue::BoolValue(right) = self.right_hand {
+                        return Ok(left && right);
+                    }
+                }
+                return Err(anyhow!("Mismatched datatypes"));
+            }
+            LogicalOperator::Or => {
+                if let LogicValue::BoolValue(left) = self.left_hand {
+                    if let LogicValue::BoolValue(right) = self.right_hand {
+                        return Ok(left || right);
+                    }
+                }
+                return Err(anyhow!("Mismatched datatypes"));
+            }
+            _ => {
+                return Err(anyhow!("Invalid operator for datatype bool"));
+            }
+        }
+    }
+
+    fn evaluate_u8(&self) -> ::anyhow::Result<bool>{
+        match self.operator {
+            LogicalOperator::Equal => {
+                return Ok(self.left_hand == self.right_hand);
+            }
+            LogicalOperator::GreaterThan => {
+                if let LogicValue::U8Value(left) = self.left_hand {
+                    if let LogicValue::U8Value(right) = self.right_hand {
+                        return Ok(left > right);
+                    }
+                }
+                return Err(anyhow!("Mismatched datatypes"));
+            }
+            LogicalOperator::LessThan => {
+                if let LogicValue::U8Value(left) = self.left_hand {
+                    if let LogicValue::U8Value(right) = self.right_hand {
+                        return Ok(left < right);
+                    }
+                }
+                return Err(anyhow!("Mismatched datatypes"));
+            }
+            LogicalOperator::GreaterThanEqualTo => {
+                if let LogicValue::U8Value(left) = self.left_hand {
+                    if let LogicValue::U8Value(right) = self.right_hand {
+                        return Ok(left >= right);
+                    }
+                }
+                return Err(anyhow!("Mismatched datatypes"));
+            }
+            LogicalOperator::LessThanEqualTo => {
+                if let LogicValue::U8Value(left) = self.left_hand {
+                    if let LogicValue::U8Value(right) = self.right_hand {
+                        return Ok(left <= right);
+                    }
+                }
+                return Err(anyhow!("Mismatched datatypes"));
+            }
+            _ => {
+                return Err(anyhow!("Invalid operator for datatype integer"));
+            }
+        }
+    }
+}
+
 impl Command {
     fn parse_insert_command(tokens: &mut Vec<String>) -> ::anyhow::Result<Command> {
         let mut state: InsertParserState = InsertParserState::IntoKeyword;
@@ -218,12 +408,93 @@ impl Command {
         Err(anyhow!("Unexpected end of input"))
     }
 
+    fn parse_logic_expression(tokens: &mut Vec<String>) -> ::anyhow::Result<LogicExpression> {
+        let mut state: LogicExpressionParserState = LogicExpressionParserState::NumberOrQuoteOrColname;
+        let mut left_hand: Option<LogicValue> = None;
+        let mut right_hand: Option<LogicValue> = None;
+        let mut operator: Option<LogicalOperator> = None;
+
+        while let Some(token) = &tokens.pop() {
+            match state {
+                LogicExpressionParserState::NumberOrQuoteOrColname => {
+                    if token == "'" {
+                        state = LogicExpressionParserState::StringValue;
+                    } else {
+                        let test = token.parse::<u8>();
+                         match test {
+                            Ok(u8_val) => {
+                                if left_hand.is_none() {
+                                    left_hand = Some(LogicValue::U8Value(u8_val)); 
+                                    state = LogicExpressionParserState::Operator;
+                                } else {
+                                    right_hand = Some(LogicValue::U8Value(u8_val)); 
+                                    return Ok(LogicExpression {left_hand: left_hand.unwrap(), right_hand: right_hand.unwrap(), operator: operator.unwrap()});
+                                } 
+                            },
+                            Err(_) => {
+                                if left_hand.is_none() {
+                                    left_hand = Some(LogicValue::ColumnName(token.to_string())); 
+                                    state = LogicExpressionParserState::Operator;
+                                } else {
+                                    right_hand = Some(LogicValue::ColumnName(token.to_string())); 
+                                    return Ok(LogicExpression {left_hand: left_hand.unwrap(), right_hand: right_hand.unwrap(), operator: operator.unwrap()});
+                                } 
+                            }, 
+                        }  
+                    }
+
+                }
+                LogicExpressionParserState::StringValue => {
+                    let mut value:  Option<LogicValue> = None;
+                    if token == "'" {
+                        value = Some(LogicValue::StringValue("".to_string()));
+                    } else {
+                        value = Some(LogicValue::StringValue(token.to_string()));
+                    }
+                    if left_hand.is_none() {
+                       left_hand = value; 
+                    } else {
+                       right_hand = value; 
+                    } 
+                    state = LogicExpressionParserState::EndQuote;
+                }
+                LogicExpressionParserState::EndQuote => {
+                    if token == "'" {
+                        if right_hand.is_none() {
+                            state = LogicExpressionParserState::Operator; 
+                        } else {
+                            return Ok(LogicExpression {left_hand: left_hand.unwrap(), right_hand: right_hand.unwrap(), operator: operator.unwrap()});
+                        } 
+                    } else {
+                        return Err(anyhow!("Expected end quote at or near {}", token));
+                    }
+                }
+                LogicExpressionParserState::Operator => {
+                    operator = match token.as_str() {
+                        "OR" => Some(LogicalOperator::Or),
+                        "AND" => Some(LogicalOperator::And),
+                        "=" => Some(LogicalOperator::Equal),
+                        ">" => Some(LogicalOperator::GreaterThan),
+                        "<" => Some(LogicalOperator::LessThan),
+                        ">=" => Some(LogicalOperator::GreaterThanEqualTo),
+                        "<=" => Some(LogicalOperator::LessThanEqualTo),
+                        _ => return Err(anyhow!("Unknown operator {}", token))
+                    };
+                    state = LogicExpressionParserState::NumberOrQuoteOrColname;
+                }
+            }
+        }
+
+        Err(anyhow!("Unexpected end of input"))
+    }
+
     fn parse_select_command(tokens: &mut Vec<String>) -> ::anyhow::Result<Command> {
         let mut state: SelectParserState = SelectParserState::ColumnName;
 
         // intermediate tmp vars
         let mut table_name = String::new();
         let mut column_names: Vec<String> = vec![];
+        let mut logic_expression: Option<LogicExpression> = None;
 
         while let Some(token) = &tokens.pop() {
             match state {
@@ -246,13 +517,24 @@ impl Command {
                 }
                 SelectParserState::TableName => {
                     table_name = token.to_string();
+                    state = SelectParserState::WhereKeywordOrSemicolon;
+                }
+                SelectParserState::WhereKeywordOrSemicolon => {
+                    if token == ";" {
+                        return Ok(Command::Select(SelectCommand { table_name, column_names, logic_expression: None }));
+                    } else if token == "WHERE" {
+                        logic_expression = Some(Self::parse_logic_expression(tokens)?);
                         state = SelectParserState::Semicolon;
+                    } else {
+                        return Err(anyhow!("Expected semicolon at or near '{}'", token));
+
+                    }
                 }
                 SelectParserState::Semicolon => {
                     if token != ";" {
                         return Err(anyhow!("Expected semicolon at or near '{}'", token));
                     } else {
-                        return Ok(Command::Select(SelectCommand { table_name, column_names }));
+                        return Ok(Command::Select(SelectCommand { table_name, column_names, logic_expression }));
                     }
                 }
             }
@@ -267,6 +549,7 @@ impl Command {
 
         // intermediate tmp vars
         let mut table_name = String::new();
+        let mut logic_expression: Option<LogicExpression> = None;
 
         while let Some(token) = &tokens.pop() {
             match state {
@@ -279,13 +562,23 @@ impl Command {
                 }
                 DeleteParserState::TableName => {
                     table_name = token.to_string();
+                    state = DeleteParserState::WhereKeywordOrSemicolon;
+                }
+                DeleteParserState::WhereKeywordOrSemicolon => {
+                    if token == ";" {
+                        return Ok(Command::Delete(DeleteCommand { table_name, logic_expression: None }));
+                    } else if token == "WHERE" {
+                        logic_expression = Some(Self::parse_logic_expression(tokens)?);
                         state = DeleteParserState::Semicolon;
+                    } else {
+                        return Err(anyhow!("Expected semicolon at or near '{}'", token));
+                    }
                 }
                 DeleteParserState::Semicolon => {
                     if token != ";" {
                         return Err(anyhow!("Expected semicolon at or near '{}'", token));
                     } else {
-                        return Ok(Command::Delete(DeleteCommand { table_name }));
+                        return Ok(Command::Delete(DeleteCommand { table_name, logic_expression }));
                     }
                 }
             }
@@ -400,4 +693,12 @@ impl Command {
 
         Err(anyhow!("Unexpected end of statement"))
     }
+    
+    pub fn le_from_string(command_str: String) -> ::anyhow::Result<LogicExpression> {
+        let mut tokens: Vec<String> = tokenizer(command_str.clone());
+        println!("{}", command_str);
+        println!("{:?}", tokens);
+        tokens.reverse();
+        return Ok(Self::parse_logic_expression(&mut tokens)?);
+    }
 }